}
private Container.Hierarchical createHierarchicalContainer(int properties,
int items, int roots) {
Container.Hierarchical c = new HierarchicalContainer();
populateContainer(c, properties, items);
if (items <= roots) {
return c;
}
// "roots" roots, each with
// "firstLevel" children, two with no children (one with childAllowed,
// one without)
// ("firstLevel"-2)*"secondLevel" children ("secondLevel"/2 with
// childAllowed, "secondLevel"/2 without)
// N*M+N*(M-2)*C = items
// items=N(M+MC-2C)
// Using secondLevel=firstLevel/2 =>
// items = roots*(firstLevel+firstLevel*firstLevel/2-2*firstLevel/2)
// =roots*(firstLevel+firstLevel^2/2-firstLevel)
// = roots*firstLevel^2/2
// => firstLevel = sqrt(items/roots*2)
int firstLevel = (int) Math.ceil(Math.sqrt(items / roots * 2.0));
int secondLevel = firstLevel / 2;
while (roots * (1 + 2 + (firstLevel - 2) * secondLevel) < items) {
// Increase something so we get enough items
secondLevel++;
}
List<Object> itemIds = new ArrayList<Object>(c.getItemIds());
int nextItemId = roots;
for (int rootIndex = 0; rootIndex < roots; rootIndex++) {
// roots use items 0..roots-1
Object rootItemId = itemIds.get(rootIndex);
// force roots to be roots even though they automatically should be
c.setParent(rootItemId, null);
for (int firstLevelIndex = 0; firstLevelIndex < firstLevel; firstLevelIndex++) {
if (nextItemId >= items) {
break;
}
Object firstLevelItemId = itemIds.get(nextItemId++);
c.setParent(firstLevelItemId, rootItemId);
if (firstLevelIndex < 2) {
continue;
}
// firstLevelChildren 2.. have child nodes
for (int secondLevelIndex = 0; secondLevelIndex < secondLevel; secondLevelIndex++) {
if (nextItemId >= items) {
break;
}
Object secondLevelItemId = itemIds.get(nextItemId++);
c.setParent(secondLevelItemId, firstLevelItemId);
}
}
}
return c;